Second receptors which the pathogenic virus causative of AIDS (HIV-1 virus) utilizes in infecting human were identified in 1996 (Yu Feng et al., Science, 272, 872-877, 1996). These two receptors are called CXCR4 and CCR5. It has been revealed that the HIV-1 virus utilizes one of the receptors for adsorption onto and entry into lymphocytes, macrophages and dendritic cells to achieve infection.
On the other hand, about 1 to 2% of Caucasians reportedly have resistance to HIV-1 virus infection and it has been revealed that this is due to a genetic defect or genetic incompleteness of the second receptors (CXCR4 and CCR5), which are chemokine receptors (Rong Liu et al., 86, 367-377, 1996).
These findings have called researchers attention to the importance of neutralization of the second receptors in the prevention of HIV-1 virus infection and, in recent years, attempts have been made to produce a neutralizing antibody capable of neutralizing the second receptors. There is no report, however, of the successful creation of such a neutralizing antibody.
Accordingly, it is an object of the present invention to provide three-dimensional antigens capable of producing, in vivo, a neutralizing antibody capable of neutralizing the second receptors from the stereoscopic viewpoint by paying attention to the loop structures of the second receptor proteins without following the conventional methods which interpret the peptides constituting the second receptors two-dimensionally. Another object is to provide AIDS vaccines which comprise such antigens as active ingredients.